1. Field of the Invention
This invention relates generally to pipe lifting and handling apparatus and more particularly to a clamping type hook mechanism capable of establishing releasable clamping engagement with the extremity of a joint of pipe to prevent inadvertent disassembly of the hook mechanism from the pipe when used in pairs to lift and handle sections of pipe.
2. Description of the Prior Art
While the present invention described herein is particularly in relation to lifting and handling joints of pipe, it is not intended that the invention be specifically limited to pipe joints. This invention is applicable to the lifting and handling of any elongated bar member and therefore the breadth of the invention is intended to include lifting and handling of elongated members such as pipes, structural members and the like. Especially in field environments such as when pipe is handled around well drilling sites, placed into or moved from various transportation systems, such as trucks, trains, pipe handling barges and the like, the pipe is typically lifted through use of a lifting bridle that extends from a lifting cable. The lifting bridle typically has two legs that extend from the lifting cable with a "C" shaped hook connected to each end of the bridle. The hooks are merely placed into the ends of joints of pipe such as drill stem, well casing and the like, and are held in place by workers until a lifting force is applied to the bridle and hooks by means of a lifting cable. After this lifting force has been applied the hooks will usually remain in place during lifting since the hooks are urged in angulated relation to the pipe by means of the lifting bridle.
Since the hooks must be manually retained in proper position as lifting force is applied, obviously the workers involved are subjected to considerable danger especially at the initial portion of the lifting operation. Since workers must hold the hooks in place in the pipe ends until lifting begins, the hands of many workers have been injured when lifting forces are applied to bridle and hook assemblies, especially when the hands of the workers are improperly positioned or under circumstances when the lifting hooks slip. It is desirable therefore to provide a pipe lifting and handling system whereby workers need not manually retain lifting mechanisms in place as lifting force is applied.
Another danger that frequently exists to the workers is the danger that the hooks will slip during a lifting operation, thereby allowing joints of pipe to be released and fall in the working area. Many workers have been injured and much property damages has resulted due to falling pipe. When pipe is being lifted or lowered in relation to pipe handling barges, such as when pipe and well casing are handled in relation to offshore well drilling rigs, the barge movement that occurs due to wave action simply compounds the severity of pipe handling problems and the danger to the workers involved. It is highly desirable that workers involved in such pipe handling operations be capable of positioning pipe lifting apparatus within pipe to be lifted and then withdrawing to a safe position during lifting of the pipe. It is also important to provide effective pipe handling apparatus that will not slip and allow the pipe to fall after being elevated.
Pipe such as drill stem and casing for well drilling and completion operations is typically threaded at the ends thereof to provide for connection of pipe joints to form pipe strings or casing strings. These threaded connections must remain undamaged during pipe handling and transportation operations because the pipe joints are required to withstand a significant amount of fluid pressure and the threads must form an efficient seal. When a pipe lifting hook slips and allows a section of pipe to fall even a few inches, the force of impact of the externally threaded ends of the pipe can severely damage the threads to the extent that the pipe joint must be returned to a manufacturing facility for rethreading operations. Further, internal pipe threads can be easily damaged if pipe lifting hooks slip during lifting. It is highly desirable therefore that pipe lifting and handling apparatus be capable of absolutely preventing pipe from falling or slipping during such handling operations. Obviously pipe handling hooks that are mechanically secured to the pipe during initial lifting and hoisting operations will greatly reduce the damage that might otherwise occur if the pipe were allowed to slip and fall. Moreover, protection for other equipment and personnel is materially enhanced if pipe lifting hooks are capable of being retained in positive mechanical assembly with the ends of pipe during all phases of lifting and handling operations.